Vintersong, the Exiled

Trample
At the beginning of your upkeep, if you've cast
a red spell this turn, put a +1/+1 counter on Vintersong, the Exiled. If Vintersong, the Exiled
has three or more +1/+1 counters on it, it gains
double strike until end of turn, and loses its
counters.
When Vintersong, the Exiled leaves the battlefield, whether by your choice or not, exile it instead.